The mechanisms of bacterial colonization of the vagina and urethra which include adherence and multiplication, and the transformation into invasive infection will be investigated. Part 1: The relative cellular activity of introitus and urethra and the relative resistance of young and mature epithelial cells; the characteristics and adherence of bacteria to introitus, urethra and bladder; normal and pathologic desquamation mechanisms; effect of chronic perineal contamination; and bacterial characteristics for adherence (pili, etc.), Part 2: The transformation of colonization to infection; the comparative roles of stasis and pressure in establishment of infection; and the role of urethritis in the sequence to vesical infection.